Assessment of BODIPY–Oxasmaragdyrin Dyads for Dye-Sensitized Solar Cells: Aromaticity, Photosensitization Capability, and Charge Transport

Abstract

Dye-sensitized solar cells (DSSC) are presented as an alternative among renewable energies where the dye plays an important role to obtain an effective device. Our goal in this work is to examine the influence of several bridging functional groups between the BODIPY and oxasmaragdyrin systems forming dyads (D), as potential components of DSSC, on the aromatic, photophysical, and charge transport properties. A set of 11 dyads made of the oxasmaragdyrin with 2,6-dimethoxyphenyl and methylamine groups in two of their meso carbons (S) and the 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY, B) moieties that differ in the binding bridge between them has been analyzed with density functional theory (DFT). The geometries were optimized with the B3LYP/6-311G­(d,p) level of theory employing D3 Grimme′s correction, and a set of six functionals (B3LYP, BHandHLYP, CAM-B3LYP, PBE0, wB97X, TPSSh) was evaluated for reference systems in time-dependent DFT calculations. We found that TPSSh presents the best agreement with the available data of UV–vis spectra, so it was used for calculation of the electronic absorption spectra of the 11 oxasmaragdyrins and 11 dyads. When the bridge between S and B consists of one (D3), two (D5), or three acetylene units (D6), a strong absorption band in the infrared region around 1000 nm can be achieved. These bands correspond to charge-separated excited states that favor a panchromatic absorption in that region. The aromaticity index NICS(0) computed at the macrocycle center ring critical point using the GIAO/B3LYP/6-311G­(d,p) level of theory shows in all these systems an aromatic character for the oxasmaragdyrin macrocycle (from −10.7 to −12.4 ppm). We also found that all dyads present a favorable electron injection toward the semiconductor TiO2 because the LUMO energy of the dyad is higher than the conduction band of the semiconductor (−4.3 eV) used in a solar cell. Besides, the HOMO energy of the dyads D3, D5, and D6 is lower than the redox potential (−4.8 eV) of a mediator as the I–/I3 – system used to recover it after circulation of electrons. Nonequilibrium Green′s function-based calculations performed for a couple of dyads, with (D6) and without (D4) a significant charge transfer band, connected to Au electrodes show that D6 was to be a better conductor, in agreement with the charge transfer results obtained from the photophysical properties. Finally, the Gibbs free energy for the formation of the dyads here investigated is calculated. All of them are shown to be exergonic reactions (ΔG solution < 0), which suggests that these systems could be synthesized.

Zn(II)-Porphyrin–Squaraine Dyads as Potential Components for Dye-Sensitized Solar Cells: A Quantum Chemical Study of Optical and Charge Transport Properties

“…For comparison purposes, we also calculated Δ G solution for D ref . The same functional (B3LYP) used for the optimization of the molecular structures were also chosen for the calculation of the Gibbs free energies, as in a previous work …”

“…It is not easy to decide because several functionals have good behavior for the electronic absorption spectra. Considering the excellent results obtained with TPSSh in previous work for the optical properties of BODIPY-oxasmaragdyrin dyads, 25 we have chosen the functional TPSSh to perform the whole study for all dyads. Other reasons consider that it produces low deviations and includes the Hartree−Fock exact exchange that allows a more suitable representation of the electron density and their properties.…”

“…The same functional (B3LYP) used for the optimization of the molecular structures were also chosen for the calculation of the Gibbs free energies, as in a previous work. 25 As can be seen in Table 5, in all cases the ΔG solution values are negative, indicating that all the synthesis of dyads is thermodynamically favorable processes. It means that all the dyads proposed in our study are stable and could be synthesized following the reaction scheme proposed by Warnan et al 29…”

BODIPY Conjugates as Functional Compounds for Medical Diagnostics and Treatment

“…According to the equation, the energy transfer quantum yield value of phthalocyanine 88 was observed (0.95), and the singlet oxygen generation yield value (0.46) characterizes 88 as a potential photosensitizer in PDT applications. Recent studies have shown the importance of oxasmaragdyrin sensitizer as a compelling material for light-energy-harvesting applications [64]. The coupling of oxasmaragdyrins with BODIPY enhances the photosensitization of 89 (Scheme 46).…”

Assessment of New Expanded Porpholactones as UV/Vis/NIR Chromophores for Dye-Sensitized Solar Cell Applications

“…In the search of materials that absorb in NIR, expanded porphyrins arise as a viable alternative due to its extended conjugation since it has more than four rings in its structure, making them excellent candidates to be applied as PDT sensitizers, NIR dyes, , NLO materials, spintronic devices, and chemical sensors . To expand the family of compounds derived from porpholactones and inspired by the work of Zhang and co-workers, this paper explores the properties of expanded porphyrin derivatives where one or two oxazolone moieties have replaced the imine rings.…”